uroguanylin and Disease-Models--Animal

Linaclotide is a minimally absorbed agonist of guanylate cyclase-C (GUCY2C or GC-C) that reduces symptoms associated with irritable bowel syndrome with constipation (IBS-C). Little is known about the mechanism by which linaclotide reduces abdominal pain in patients with IBS-C.. We determined the effects of linaclotide on colonic sensory afferents in healthy mice and those with chronic visceral hypersensitivity. We assessed pain transmission by measuring activation of dorsal horn neurons in the spinal cord in response to noxious colorectal distention. Levels of Gucy2c messenger RNA were measured in tissues from mice using quantitative reverse transcription polymerase chain reaction and in situ hybridization. We used human intestinal cell lines to measure release of cyclic guanosine-3',5'-monophosphate (cGMP) by linaclotide. We performed a post-hoc analysis of data from a phase III, double-blind, parallel-group study in which 805 patients with IBS-C were randomly assigned to groups given an oral placebo or 290 μg linaclotide once daily for 26 weeks. We quantified changes in IBS-C symptoms, including abdominal pain.. In mice, linaclotide inhibited colonic nociceptors with greater efficacy during chronic visceral hypersensitivity. Intra-colonic administration of linaclotide reduced signaling of noxious colorectal distention to the spinal cord. The colonic mucosa, but not neurons, was found to express linaclotide's target, GC-C. The downstream effector of GC-C, cGMP, was released after administration of linaclotide and also inhibited nociceptors. The effects of linaclotide were lost in Gucy2c(-/-) mice and prevented by inhibiting cGMP transporters or removing the mucosa. During 26 weeks of linaclotide administration, a significantly greater percentage of patients (70%) had at least a 30% reduction in abdominal pain compared with patients given placebo (50%).. We have identified an analgesic mechanism of linaclotide: it activates GC-C expressed on mucosal epithelial cells, resulting in the production and release of cGMP. This extracellular cGMP acts on and inhibits nociceptors, thereby reducing nociception. We also found that linaclotide reduces chronic abdominal pain in patients with IBS-C.

Topics: Abdominal Pain; Adult; Aged; Aged, 80 and over; Animals; Caco-2 Cells; Cell Line; Colon; Cyclic GMP; Disease Models, Animal; Double-Blind Method; Female; Guanylate Cyclase; Humans; Irritable Bowel Syndrome; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Middle Aged; Natriuretic Peptides; Nociceptors; Peptides; Receptors, Atrial Natriuretic Factor; Receptors, Enterotoxin; Receptors, Guanylate Cyclase-Coupled; Receptors, Peptide; Treatment Outcome; Trinitrobenzenesulfonic Acid

The natural hormone uroguanylin regulates intestinal fluid homeostasis and bowel function through activation of guanylate cyclase-C (GC-C), resulting in increased intracellular cyclic guanosine-3',5'-monophosphate (cGMP). We report the effects of uroguanylin-mediated activation of the GC-C/cGMP pathway in vitro on extracellular cGMP transport and in vivo in rat models of inflammation- and stress-induced visceral hypersensitivity. In vitro exposure of intestinal Caco-2 cells to uroguanylin stimulated bidirectional, active extracellular transport of cGMP into luminal and basolateral spaces. cGMP transport was significantly and concentration dependently decreased by probenecid, an inhibitor of cGMP efflux pumps. In ex vivo Ussing chamber assays, uroguanylin stimulated cGMP secretion from the basolateral side of rat colonic epithelium into the submucosal space. In a rat model of trinitrobenzene sulfonic acid (TNBS)-induced visceral hypersensitivity, orally administered uroguanylin increased colonic thresholds required to elicit abdominal contractions in response to colorectal distension (CRD). Oral administration of cGMP mimicked the antihyperalgesic effects of uroguanylin, significantly decreasing TNBS- and restraint stress-induced visceromotor response to graded CRD in rats. The antihyperalgesic effects of cGMP were not associated with increased colonic spasmolytic activity, but were linked to significantly decreased firing rates of TNBS-sensitized colonic afferents in rats in response to mechanical stimuli. In conclusion, these data suggest that the continuous activation of the GC-C/cGMP pathway along the intestinal tract by the endogenous hormones guanylin and uroguanylin results in significant reduction of gastrointestinal pain. Extracellular cGMP produced on activation of GC-C is the primary mediator in this process via modulation of sensory afferent activity.

Topics: Acetylcholine; Acetylglucosamine; Adenocarcinoma; Animals; Cell Differentiation; Cell Line, Tumor; Colitis; Colon; Colorectal Neoplasms; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Electric Stimulation; Female; Gastrointestinal Diseases; Gene Expression Regulation, Neoplastic; Guanylate Cyclase; Humans; Hyperalgesia; Intestinal Mucosa; Male; Mast Cells; Morphine; Multidrug Resistance-Associated Proteins; Natriuretic Peptides; Organic Anion Transporters, Sodium-Independent; Peroxidase; Rats; Rats, Sprague-Dawley; Rats, Wistar; Restraint, Physical; RNA, Messenger; Signal Transduction; Trinitrobenzenesulfonic Acid; Visceral Pain

Midbrain dopamine neurons regulate many important behavioral processes, and their dysfunctions are associated with several human neuropsychiatric disorders such as attention deficit hyperactivity disorder (ADHD) and schizophrenia. Here, we report that these neurons in mice selectively express guanylyl cyclase-C (GC-C), a membrane receptor previously thought to be expressed mainly in the intestine. GC-C activation potentiates the excitatory responses mediated by glutamate and acetylcholine receptors via the activity of guanosine 3',5'-monophosphate-dependent protein kinase (PKG). Mice in which GC-C has been knocked out exhibit hyperactivity and attention deficits. Moreover, their behavioral phenotypes are reversed by ADHD therapeutics and a PKG activator. These results indicate important behavioral and physiological functions for the GC-C/PKG signaling pathway within the brain and suggest new therapeutic targets for neuropsychiatric disorders related to the malfunctions of midbrain dopamine neurons.

Topics: Amphetamine; Animals; Attention; Attention Deficit Disorder with Hyperactivity; Behavior, Animal; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Disease Models, Animal; Dopamine; Enzyme Activation; Gastrointestinal Hormones; Glycine; Impulsive Behavior; Ligands; Mice; Mice, Inbred C57BL; Mice, Knockout; Motor Activity; Natriuretic Peptides; Neurons; Patch-Clamp Techniques; Receptors, Enterotoxin; Receptors, Glutamate; Receptors, Guanylate Cyclase-Coupled; Receptors, Muscarinic; Receptors, Peptide; Resorcinols; Signal Transduction; Substantia Nigra; Ventral Tegmental Area

Uroguanylin induces natriuresis and diuresis in vivo as well as in vitro and is found mainly in the intestine and the kidney. However, the roles of uroguanylin in nephrotic syndrome, which is associated with sodium and water retention, have not been determined. Therefore, changes in the urine and plasma concentration of immunoreactive uroguanylin (ir-uroguanylin) and its mRNA expression in the kidney and intestine were examined using rats with puromycin aminonucleoside (PAN)-induced nephrosis. Male Sprague-Dawley rats were separated into control and nephrotic groups, and then the urinary excretion of sodium, protein, and ir-uroguanylin was examined over time. The plasma levels and renal and intestinal mRNA expression of uroguanylin at the periods of sodium retention and remarkable natriuresis also were evaluated. The sequential changes of urinary ir-uroguanylin excretion in the nephrotic group were similar to those of urinary sodium excretion. When the urinary excretion of ir-uroguanylin and sodium peaked, the plasma level of ir-uroguanylin also increased compared with that of the control group. Uroguanylin mRNA expression in the kidney increased during the period of sodium retention and then decreased during the period of remarkable natriuresis. Uroguanylin mRNA expression in the small intestines of control and nephrotic rats were identical. However, in a unilateral PAN-induced proteinuria, uroguanylin expression significantly increased in the PAN-perfused kidney compared with that in the opposite kidney. Considering the natriuretic effect of uroguanylin, these results suggested that uroguanylin plays an important role as a natriuretic factor in nephrotic syndrome via both the circulation and the kidney itself.

Topics: Animals; Atrial Natriuretic Factor; Base Sequence; Biomarkers; Disease Models, Animal; Male; Molecular Sequence Data; Natriuresis; Natriuretic Peptides; Nephrotic Syndrome; Peptides; Probability; Puromycin Aminonucleoside; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

Uroguanylin is a peptide hormone that regulates sodium excretion by the kidney when excess NaCl is consumed. A new study demonstrates that mice deficient in uroguanylin have blunted urinary sodium excretion responses to oral sodium loads in addition to elevated blood pressure (see related article beginning on page 1244). A physiological role for uroguanylin is discussed, linking the intestine and kidney in an endocrine axis for the maintenance of sodium balance.

Topics: Amino Acid Sequence; Animals; Disease Models, Animal; Gastrointestinal Hormones; Humans; Mice; Molecular Sequence Data; Natriuretic Peptides; Peptides; Sodium; Water-Electrolyte Balance